Suction box arrangement for a paper machine

ABSTRACT

THE COVER OF A SUCTION BOX CONSISTS OF UNITS JUXTAPOSED OVER THE WIDTH OF THE MACHINE AND INDIVIDUALLY FASTENED TO THE RIGID BASE OF THE BOX. EACH UNIT CONSISTS OF A GROUP OF PARALLEL RAIL SECTIONS SPACEDLY JUTAPOSED IN THE DIRECTION IN WHICH THE FOURDRINER WIRE OR SCREEN MOVES OVER THE COVER AND OF ONE OR MORE SUPPORTING ELEMENTS SECURED TO ALL THE SECTIONS IN THE GROUP AND CONNECTING THE SAME INTO A UNIT.

June 26, 1973 H. JUD F 'AL SUCTION Box ARRANGEMENT FOR A PAPER MACHINE Filed June 15, 1971 2 Sheets-Sheet 1 FIG. 2

INVENTORS v June 26, 1973 JUD ET AL 3,741,866

SUCTION BOX ARRANGEMENT FOR A PAPER MACHINE Filed June 15, 1971 2 Sheets-Sheet 2 m k u Q V LL. 4 1:4

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United States Patent Oflice 3,741,866 Patented June 26, 1973 3,741,866 SUCTION BOX ARRANGEMENT FOR A PAPER MACHINE Hans Jud, Esslingen, Sulzgries, Manfred Nussbaum, Plochingen, and Karl-Dieter Fuchs, Ebersfach, Fils, Germany, assignors to Feldmuhle Anlagenund Produktionsgesellschaft mit beschrankter Haftung, Dusseldorf, Germany Filed June 15, 1971, Ser. No. 153,384 Claims priority, application Germany, June 16, 1970, P 20 29 617.7 Int. Cl. D21f 1/48 US. Cl. 162-374 Claims ABSTRACT OF THE DISCLOSURE The cover of a suction box consists of units juxtaposed over the width of the machine and individually fastened to the rigid base of the box. Each unit consists of a group of parallel rail sections spacedly juxtaposed in the direction in which the Fourdrinier wire or screen moves over the cover and of one or more supporting elements secured to all the sections in the group and connecting the same into a unit.

This invention relates to paper machines of the Fourdinier type, and particularly to suction boxes.

Suction boxes are arranged across the width of the machine in the wet section of the same in which water is withdrawn from the stuff deposited on the travelling Fourdrinier wire or screen, and a web of interengaged fibers is formed thereby. The invention is concerned more specifically with an improved suction box cover.

It is known to provide a suction box with a cover essentially consisting of rails which extend over the full width of the machine and are juxtaposed in spacedly parallel relationship in a common plane on the upwardly open side of the hollow suction box. The rails support the rapidly travelling Fourdrinier wire while the water is drawn from the deposited stuff through the wire and the gaps between the rails by a vacuum produced in the box by means of a connected pump. Modern paper machines may have a width of 25 feet, and it is not practical to make rails of such length from the preferred materials which are sintered ceramics having a hardness not substantially below 7 on the Mohs scale, such as alumina and silicon carbide. The rails are therefore assembled from a plurality of longitudinal sections, typically 8" to 12" long.

The rails when made of the preferred very hard materials greatly increase the life of the Fourdrinier wire if they are properly installed. The wire engaging surfaces of all sections in a cover assembly must be located in a common plane to have the desired effect. Although they wear very slowly, they must be replaced from time to time because of wear and because of accidental damage. It is difiicult, time consuming, and therefore costly to restore the rail sections of known suction box arrangements to the proper alignment of their wire engaging surfaces, and laborious filing of the sections was frequently resorted to heretofore.

It has now been found that the cost of replacing the rail sections of ceramic material can be reduced greatly if respective sections of the several directly juxtaposed rail elements are made longitudinally coextensive so as to constitute groups of sections, and one or more supporting elements are associated with each group, the supporting element or elements being elongated transversely of the direction of rail elongation. The several sections of the group are secured to the associated supporting element and thereby connected to form a supporting element.

Each unit is individually fastened to the rigid base of the suction box and constitutes the sole connection between the rail sections of the unit and the suction box base.

Other features and many of the attendant advantages of this invention will readily be appreciated as the invention becomes better understood from the following description of preferred embodiments when considered in connection with the appended drawing in which:

FIG. 1 is a fragmentary view of a suction box arrangement according to the invention in side elevation and partly in section;

FIG. 2 shows the apparatus of FIG. 1 in section on the line II-II;

FIG. 3 shows another suction box arrangement of the invention in fragmentary side elevation and partly in section; and

FIG. 4 illustrates a modification of the device of FIG. 1 in partly sectional side elevation.

Referring now to the drawing in detail, and initially to FIGS. 1 and 2, there is shown only as much of an otherwise conventional Fourdrinier type paper machine as is necessary for an understanding of the invention. Only portions of the suction box base 4 are illustrated. It is connected with a vacuum line 4' for withdrawing or water from a fiber dispersion carried by a Fourdrinier wire or screen, not shown, which travels over the cover of the box with which this invention is more specifically concerned.

The base 4 of the suction box extends over the entire width of the machine and carries a row of cover units of which only one is shown. Each unit has a rigid, metallic supporting frame formed by two flat bars 6, 7 which are the principal supporting element of the unit and are elongated in the direction of screen travel, and two round traverse rods 8, 9 connecting the bars 6, 7.

One of the narrow longitudinal faces of each bar 6, 7 rests on the rigid box base 4. The other narrow face is ground to a knife edge 1. A notch 15 is formed in each longitudinal end of each bar 6, 7 in such a manner that a projection 2 extends into the notch adjacent the base 4. A screw 5 has its head in each of the notches 15 and holds a clamp 3 against the projection 2, the shank of the screw 5 being threadedly received in the base 4. The position of each bar 6, 7 is thus precisely defined relative to the paper machine frame by the rigid box base 4 to which the bars 6, 7 are fatsened by the screws 5.

Lugs 10 are welded to the knife edge 1 of each bar 6, 7 in longitudinally spaced relationship so as to project toward a corresponding lug 10 on the other knife edge, as is best seen in FIG. 2. A slot 11 in each lug 10 is longitudinally aligned with a similar slot in the corresponding lug on the other knife edge 1. A rail section 12 is attached to each pair of lugs 10 by screws 14 partly received in the slots 11 and partly in threaded blind holes 13 in the lower edges of the rail section.

The cross section of each rail section is a parallelogram which presents an acutely oblique corner to the screen for wiping liquid from the underside of the screen, as is known in itself. The section consists of sintered aluminum oxide, and the threaded holes 13 are formed in the section prior to sintering, and are of sufficient size to receive not only the screws 14 after sintering but also helical metal springs, not shown, which form female thread inserts for engagement with the screws 14.

The screws 5 are readily accessible on the assembled suction box so that each unit essentially consisting of the bars 6, 7, rods 8, 9, and rail sections 12 may be individually removed from the rigid base 4 by means of a wrench. The screws 14 which secure the sections 12 to the supporting elements then become accessible, and each of the sections 12 may be released individually.

The distance of the bottom surfaces of the rail sections 12 from the top surface of the box base 4 is determined by the spacing of the lugs from the lower edges of the bars 6, 7, and can be set once and for all during welding of the lugs 10 to the bars 6, 7 and by grinding. When new rail sections 12 replace a Worn or otherwise inoperative group of sections 12, their screen engaging top faces can be ground to a precisely reproducible level relative to the top surface of the base 4 prior to installation by means of a surface grinder of a type commonly available in machine shops since the rail sections are only one foot long or less. Yet, a multiplicity of the units described, when installed in logitudinally aligned condition of their sections on the base 4, have screen engaging surfaces which are located precisely in a common plane parallel to the top of the base 4 without requiring further adjustment, secondary grinding, or filing.

Because the rail sections 12 are secured on the supporting bars 6, 7 by means of screws 14 entering blind bores in the section bottoms, the securing arrangement cannot produce irregularities in the web produced on the screen travelling over the top surfaces of the rail sections. Such irregularities would be produced by the supporting bars 6, 7 if their tops were not ground to the illustrated shapes of knife edges. The rods 8, 9 have been found not to produce any undesirable effect on the web. They may be omitted if the greater rigidity which they impart to the supporting structure is not needed, as with relatively heavy and short rail sections 12. With very short sections, a single supporting bar may be adequate.

In the modified suction box arrangement illustrated in FIG. 3, the rail sections 21, closely analogous to the aforedescribed sections 12, are formed with bores 26 extending between their wide longitudinal faces 24 in the longitudinal median plane of the sections. Each bore 26 receives a cylindrically tubular sleeve 23 with enough clearance to provide space for a non-illustrated layer of epoxy cement which fixedly fastens the sleeve 23 in the bore 26. Each sleeve 23 projects beyond the opposite faces 24.

A supporting rod 22 is received in the sleeves 23 and in tubular spacers 25 of the same internal and external diameter as the sleeves, and also in bores of brackets 28 which are welded to the base of the suction box, not otherwise shown in FIG. 3. The ends of the rod 22 project beyond the brackets 28, are threaded, and carry nuts 27.

When the nuts 27 are tightened, the sleeves 23 in each rail section 21 abuttingly engage either the corresponding sleeve of another rail section or an interposed spacer 25, and the nuts thus secure the rail sections in a fixed position on the supporting rod 22 and simultaneously fasten the entire unit to the base of the suction box. It will be appreciated that the rod 22, sleeves 23, bores 26, spacers 25 and brackets 28 may be duplicated along the length of each group of rail sections 21 as often as may be necessary to give the desired rigidity to the unit.

It is a particular advantage of the units of the type shown in FIG. 3 that they may be reversed if the screen engaging faces are worn to present new faces in the proper position to the screen. The downtime of the paper machine, an important cost factor, necessary for thus renewing the suction box cover is minimal.

If replacement of individual rail sections of a unit is not important, the arrangement of lugs 10, screws 14, and blind threaded bores 13 described above with reference to FIG. 2 may be replaced by the much simpler and inexpensive securing arrangement shown in FIG. 4. Except as described otherwise, the rail sections 31 shown in FIG. 4 are identical with the afore-described sections 12, 21, and the supporting element 32 is identical with the bars 6, 7.

Blind holes in the knife dege of the bar 32 and in the bottom face of each rail section 31 receive respective ends of split pins 33 and are otherwise filled with a layer 34 of epoxy cement which fixedly fastens the pin 33 to the rail section and to the supporting bar, and thereby fixedly fastens the bar to the sections. To provide greater rigidity to the unit, a body 35 of epoxy cement attaches the underside of each rail section to the knife edge of the bar 32.

All joints which might permit white water to reach the epoxy cement layers shown in FIGS. 3 and 4, and all exposed epoxy cement surfaces are covered with a layer of chlorinated rubber lacquer too thin to permit pictorial representation. When so protected, commercially available epoxy cements have been found to perform well over extended periods in the suction box arrangements of the invention even when used in heavy layers. Such layers permit precise locating of metallic inserts, such as the sleeves 23 and the pins 33 in oversized openings of sintered alumina bodies. The openings must be formed prior to sintering, and they need not be ground to precise dimensions after sintering if the alumia body and the metallic insert are held in a jig while the cement sets.

It is a common advantage of the several embodiments of the invention described hereinabove that they permit individual units including each a group of rail sections to be replaced quickly, and that the substitute unit when installed is automatically aligned with the other units present without requiring secondary machining of the sections nor other adjustments that could not be performed by relatively unskilled personnel.

The rail sections may be juxtaposed as closely in each unit as may be desired or required. The sections therefore can give adequate support to a very rapidly travelling screen exposed to atmospheric pressure on one side and exposed to a practically full vacuum on the other side and prevent sagging of the screen between adjacent rail sections that would seriously shorten the useful life of the screen.

It should be understood, of course, that the foregoing disclosure relates only to preferred embodiments of the invention, and that it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purpose of the disclosure which do not depart from the spirit and scope of the appended claims.

We claim:

1. In a suction box arrangement for a paper machine including a rigid, hollow base having a side open in an upward direction and engaging means mounted on said base and extending across said open side for engagement with the Fourdrinier screen of said machine while said screen travels in a predetermined direction, the improvement in said engaging means which comprises:

(a) a plurality of engaging units offset from each other, each unit including (1) a group of elongated, longitudinally coextensive rail sections juxtaposed in a common plane in spacedly parallel relationship, each pair of directly juxtaposed sections defining a gap therebetween, said rail sections essentially consisting of sintered ceramic material having a hardness not substantially smaller than 7 on the Mohs scale,

(2) at least one supporting element elongated transversely of the direction of elongation of said sections, and

(3) securing means securing each section of said group to said at least one supporting element; and

(b) a plurality of fastening means respectively associated with said units,

(1) said fastening means each fastening the at least one supporting element of the associated unit to said base and constituting the sole connection between the rail sections of said associated unit and said base, whereby each unit may be released individually from said base by releasing the associated fastening means,

(2) said fastening means fastening the associated rail section of each unit is longitudinally aligned with respective rail sections of other units, the aligned rail sections jointly constituting a rail element extending across said open side and elongated transversely to said predetermined direction.

2. In an arrangement as set forth in claim 1, said securing means including a plurality of threaded fastener members respectively engaging each of said sections and an associated supporting element.

3. In an arrangement as set forth in claim 1, each section of said group being formed with a bore transversely therethrough, said securing means including a tubular member being fixedly fastened in said bore and respective longitudinal portions of said supporting element being received in said tubular members.

4. In an arrangement as set forth in claim 3, said bore connecting respective opposite, longitudinal faces of said section, said tubular member projecting outward of said bore beyond each of said faces.

5. In an arrangement as set forth in claim 3, a tubular spacer member longitudinally interposed on said supporting element between the tubular members associated with two of said elements longitudinally juxtaposed on said supporting element.

6. In an arrangement as set forth in claim 3, said section having a longitudinal median plane through said bore.

7. In an arrangement as set forth in claim 3, said fastening means fastening the longitudinally terminal portions of said supporting element to said base.

8. In an arrangement as set forth in claim 1, said securing means including a pin member received in respective recesses of each section and of the associated supporting element.

9. In an arrangement as set forth in claim 8, a layer of cement in said recess of the supporting element and fixedly fastening said pin member to said supporting ele ment.

10. In an arrangement as set forth in claim 9, a layer of cement in said recess of each section and fixedly fastening said pin member to said section.

References Cited UNITED STATES PATENTS 1,826,735 10/1931 Cofrin 162-352 2,740,332 4/1956 Van Ryzin 162-374 3,265,560 8/1966 Sager 162-374 1,534,854 8/1925 Lewis 162-374 2,408,176 9/1946 Prouly 162-374 3,266,977 8/ 1966 Gatke 162-374 S. LEON BASHORE, Primary Examiner R. V. FISHER, Assistant Examiner US. Cl. X.R. 162-352 

